If greenhouse gas emissions continue the warming will also continue, with temperatures projected to increase by 1.4 °C to 5.8 °C between 1990 and 2100.[A] Accompanying this temperature increase will be increases in some types of extreme weather and a projected sea level rise.[5] The balance of impacts of global warming become significantly negative at larger values of warming.[6]

These findings are recognized by the national science academies of all the major industrialized nations.[7]

Each scientist listed here has published at least one peer-reviewed article in the broad field of natural sciences, although not necessarily in a field relevant to climatology.[B] Since the publication of the IPCC Third Assessment Report, each has made a clear statement in his or her own words (as opposed to the name being found on a petition, etc.) disagreeing with one or more of the report's three main conclusions. Their views on climate change are usually described in more detail in their biographical articles. As of August 2012[update], fewer than 10 of the statements in the references for this list are part of the peer-reviewed scientific literature. The rest are statements from other sources such as interviews, opinion pieces, online essays and presentations.

Scientists questioning the accuracy of IPCC climate projections

These scientists have said that it is not possible to project global climate accurately enough to justify the ranges projected for temperature and sea-level rise over the next century. They may not conclude specifically that the current IPCC projections are either too high or too low, but that the projections are likely to be inaccurate due to inadequacies of current global climate modeling.

These scientists have said that the observed warming is more likely to be attributable to natural causes than to human activities. Their views on climate change are usually described in more detail in their biographical articles.

Notes

^ In its 2007 assessment report, IPCC projected likely temperature rise for various hypothetical levels of future greenhouse gas emissions, known as "emissions scenarios". They reported that during the 21st century the global surface temperature is likely to rise a further 1.1 to 2.9 °C (2.0 to 5.2 °F) for the lowest emissions scenario used in the report, and 2.4 to 6.4 °C (4.3 to 11.5 °F) for the highest.[145]

^ The compilation criteria for including scientists in the list is that they are relevant enough to have their own Wikipedia article, according to Wikipedia's notability guidelines.

^Epstein, Ethan (13 January 2014). "What Catastrophe?". The Weekly Standard. Retrieved 31 October 2014. Nor, of course, is he the only skeptic with serious scientific credentials... famed physicist Freeman Dyson are among dozens of scientists who have gone on record questioning various aspects of the IPCC’s line on climate change

^Koonin, Steven (September 2014). "Climate Science Is Not Settled". The Wall Street Journal. Retrieved 13 October 2014. [Many open questions] are not ″minor″ issues to be ″cleaned up″ by further research. Rather, they are deficiencies that erode confidence in the computer projections. [...They are] fundamental challenges to our understanding of human impacts on the climate, and they should not be dismissed with the mantra that 'climate science is settled.' While the past two decades have seen progress in climate science, the field is not yet mature enough to usefully answer the difficult and important questions being asked of it.

^"The Climate Science Isn't Settled", The Wall Street Journal online, November 30, 2009, Claims that climate change is accelerating are bizarre. [...] The quality of the data is poor [...] The general support for warming is based not so much on the quality of the data, but rather on the fact that there was a little ice age from about the 15th to the 19th century.

^Epstein, Ethan (13 January 2014). "What Catastrophe?". The Weekly Standard. Retrieved 31 October 2014. But Lindzen, plainly, is different. He can’t be dismissed. Nor, of course, is he the only skeptic with serious scientific credentials.

^Milloy, Steven (21 November 2007). "U.N. Climate Distractions". Fox News Channel. Retrieved 13 February 2014. A new temperature reconstruction for the past 2,000 years created by Craig Loehle of the National Council for Air and Stream Improvement indicates that, 1,000 years ago, globally averaged temperature was about 0.3 degrees Celsius warmer than the current temperature.

^Paltridge, Garth (2009). the Climate Caper. Connor Court Publishing. ISBN978-1-921421-25-9. There are good and straightforward scientific reasons to believe that the burning of fossil fuel and consequent increase in atmospheric carbon dioxide will lead to an increase in the average temperature of the world above that which would otherwise be the case. Whether the increase will be large enough to be noticeable is still an unanswered question.

^Peter Stilbs and Åke Ortmark (12 January 2014), Expressen, gå inte på klimatbluffen, IPCC gör ingen egen forskning, utan söker som grupp stöd för en given hypotes - att koldioxiden har en avgörande betydelse för jordens framtida klimat. Detta är egentligen ogörligt, då ingen ännu har klarlagt klimatsystemets naturliga variationer. Enligt de vetenskapliga principer som växt fram under hundratals år tyder de senaste 20 årens observationer snarare på att hypotesen är falsk. (Own translation to English: The IPCC does not make its own research, but is a group searching for a given hypothesis – that carbon dioxide is crucial for the earth’s future climate. This is actually impossible since nobody has yet clarifed the climate system’s natural variability. According to the scientific principles that have developed over hundreds of years, the last 20 years of observations rather indicate that the hypothesis is false.)

^Global Warming Is Not A Crisis, It is claimed, on the basis of computer models, that this should lead to 1.1 – 6.4 C warming. What is rarely noted is that we are already three-quarters of the way into this in terms of radiative forcing, but we have only witnessed a 0.6 (+/-0.2) C rise, and there is no reason to suppose that all of this is due to humans.

^Tennekes, Hendrik. "A Skeptical View of Climate Models". The blind adherence to the harebrained idea that climate models can generate 'realistic' simulations of climate is the principal reason why I remain a climate skeptic.

^Delingpole, James (16 June 2012). "It's no wonder the world's cooling on climate change". Daily Mail. Retrieved 1 November 2014. leading German green - former activist and Hamburg state environment senator Prof Fritz Vahrenholt. The evidence for man-made global warming is looking shakier by the day, Germany's answer to Jonathon Porritt or George Monbiot admitted. Far more likely a culprit is the sun.

^"Change climate change!". Hindustan Times. 19 January 2010. Retrieved 1 November 2014. A Russian astronomer named Khabibullo Abdusamatov from St Petersburg has predicted the next ice age will start between 2035 and 2045 due to a decline in solar activity

^"A little warming, a lot of hysteria". Washington Times. 11 April 2006. Retrieved 1 November 2014. professor [Robert Carter], writing in the London Daily Telegraph, does not dispute the evidence that we’re in an era of rising temperatures. Who does? But he suggests that man exhibits considerable hubris — insolence, even — if he imagines that he’s responsible.

^Easterbrook, Don (22–25 October 2006). "THE CAUSE OF GLOBAL WARMING AND PREDICTIONS FOR THE COMING CENTURY". Philadelphia Annual Meeting. Retrieved 31 August 2012. Because the warming periods in these oscillations [of glaciers] occurred well before atmospheric CO2 began to rise rapidly in the 1940s, they could not have been caused by increased atmospheric CO2, and global warming since 1900 could well have happened without any effect of CO2. If the cycles continue as in the past, the current warm cycle should end soon[...]

^Epstein, Ethan (13 January 2014). "What Catastrophe?". The Weekly Standard. Retrieved 31 October 2014. Nor, of course, is he the only skeptic with serious scientific credentials... William Happer, professor of physics at Princeton... among dozens of scientists who have gone on record questioning various aspects of the IPCC’s line on climate change

^Halfdan Carstens (2013). "Klimatolog i hardt vær". Retrieved January 9, 2014. Based on my own observations of how the climate varies naturally, I am skeptical of the CO2 hypothesis (own translation from Norwegian)

^Wibjörn Karlén (January 7, 2010). "Lilla istiden kan redan vara här". Retrieved January 16, 2014. After a long time of studying climate variations, I have come to the conclusion that the space weather suggests that we are more likely heading towards a colder period than a warmer. (own translation from Swedish)

^Legates, David (May 2006). "Climate Science: Climate Change and Its Impacts". National Center for Policy Analysis. Retrieved 31 August 2012. About half of the warming during the 20th century occurred prior to the 1940s, and natural variability accounts for all or nearly all of the warming.

^Silvey, Janese (5 March 2012). "Professor details role as climate consultant". Columbia Tribune. Retrieved 15 April 2014. There's no doubt the climate is changing; that's a given," he said. "But the question is: What's causing it. Is it mankind alone, which a lot of people say? Is it some mix of man and nature? Or is it nature? I would say nature is mostly responsible. There may be a role for man in there somewhere, but how much, I don't know.

^"He's in the hot seat". Edmonton Journal. 23 September 2007. Retrieved 31 October 2014. The main driver of climate change, [Tim Patterson] believes, is a combination of solar changes (well-known cycles of the sun's intensity) as well as cosmic rays.

^Robinson, Arthur B. (1997). "Science Has Spoken: Global Warming is a Myth". Dow Jones & Company. Retrieved 18 February 2014. we needn't worry about human use of hydrocarbons warming the Earth. We also needn't worry about environmental calamities, even if the current, natural warming trend continues: After all the Earth has been much warmer during the past 3,000 years without ill effects.

^Segalstad, Tom. "What is CO2 – friend or foe?". Retrieved July 4, 2009. The IPCC's temperature curve (the so-called 'hockey stick' curve) must be in error [...] All measurements of solar luminosity and 14C isotopes show that there is at present an increasing solar radiation which gives a warmer climate

^"Testimony of Roy W. Spencer". before the Senate Environment and Public Works Committee. 22 July 2008. Retrieved 31 August 2012. I predict that [scientists will realise] most of the climate change we have observed is natural, and that mankind’s role is relatively minor

^Svensmark, Henrik (2007). "Cosmoclimatology: a new theory emerges" (PDF). Astronomy & Geophysics48 (1): 18–24. Retrieved December 19, 2011. The case for anthropogenic climate change during the 20th century rests primarily on the fact that concentrations of carbon dioxide and other greenhouse gases increased and so did global temperatures. Attempts to show that certain details in the climatic record confirm the greenhouse forcing (e.g. Mitchell et al. 2001) have been less than conclusive. By contrast, the hypothesis that changes in cloudiness obedient to cosmic rays help to force climate change predicts a distinctive signal that is in fact very easily observed, as an exception that proves the rule.

^Tomlinson, Stuart (21 February 2008). "Update: Controversial "State Climatologist" Steps Aside". OregonLive.com. Retrieved 20 March 2014. Taylor said he believes climate change is a combination of natural factor and human factors. "I don't deny that human activities affect climate change," he said. "But I believe up to now, natural variations have played a more important role than human activities.

^Veizer, Ján (2005). "Celestial Climate Driver: A Perspective from Four Billion Years of the Carbon Cycle". Geoscience Canada. 1 32. Retrieved 26 August 2012. At this stage, two scenarios of potential human impact on climate appear feasible: (1) the standard IPCC model that advocates the leading role of greenhouse gases, particularly of CO2, and (2) the alternative model that argues for celestial phenomena as the principal climate driver. The two scenarios are likely not even mutually exclusive, but a prioritization may result in different relative impact. Models and empirical observations are both indispensable tools of science, yet when discrepancies arise, observations should carry greater weight than theory. If so, the multitude of empirical observations favours celestial phenomena as the most important driver of terrestrial climate on most time scales, but time will be the final judge.

^Syun-Ichi, Akasofu (June 15, 2007). "On the Fundamental Defect in the IPCC’s Approach to Global Warming Research by Syun-Ichi Akasofu". Climate Science: Roger Pielke Sr. wordpress.com. Retrieved 31 August 2012. [T]he method of study adopted by the International Panel of Climate Change (IPCC) is fundamentally flawed, resulting in a baseless conclusion: Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. Contrary to this statement ..., there is so far no definitive evidence that 'most' of the present warming is due to the greenhouse effect. ... [The IPCC] should have recognized that the range of observed natural changes should not be ignored, and thus their conclusion should be very tentative. The term 'most' in their conclusion is baseless.

^"Climat: la prévention, oui, la peur, non" (in French). L'Express. May 10, 2006. Archived from the original on November 17, 2006. Retrieved August 26, 2011. :The increase in the CO2 content of the atmosphere is an observed fact and mankind is most certainly responsible. In the long term, this increase will without doubt become harmful, but its exact role in the climate is less clear. Various parameters appear more important than CO2. Consider the water cycle and formation of various types of clouds, and the complex effects of industrial or agricultural dust. Or fluctuations of the intensity of the solar radiation on annual and century scale, which seem better correlated with heating effects than the variations of CO2 content.

^Balling, Robert (September 2003). "The Increase in Global Temperature: What it Does and Does Not Tell Us". George C. Marshall Institute. [I]t is very likely that the recent upward trend [in global surface temperature] is very real and that the upward signal is greater than any noise introduced from uncertainties in the record. However, the general error is most likely to be in the warming direction, with a maximum possible (though unlikely) value of 0.3 °C. ... At this moment in time we know only that: (1) Global surface temperatures have risen in recent decades. (2) Mid-tropospheric temperatures have warmed little over the same period. (3) This difference is not consistent with predictions from numerical climate models.

^Christy, John R.; Douglass, David H. (2009). "Limits on CO2 Climate Forcing from Recent Temperature Data of Earth" (PDF). Energy & Environment20: 177–189. doi:10.1260/095830509787689277. Retrieved June 17, 2011. ...the data show a small underlying positive trend that is consistent with CO2 climate forcing with no-feedback. [...] There is disagreement in regard to the validity of the global warming hypothesis that states that there are positive feedback processes leading to gains g that are larger than 1, perhaps as large as 3 or 4. However, recent studies suggest that the values of g is much smaller.

^Christy, John (November 1, 2007). "My Nobel Moment". Wall Street Journal. Retrieved November 2, 2007. ...I see neither the developing catastrophe nor the smoking gun proving that human activity is to blame for most of the warming we see. Rather, I see a reliance on climate models (useful but never "proof") and the coincidence that changes in carbon dioxide and global temperatures have loose similarity over time.

^Petr Chylek (April 2002). "A Long Term Perspective on Climate Change". Heartland.org. Archived from the original on September 29, 2007. Retrieved August 26, 2011. Carbon dioxide should not be considered as a dominant force behind the current warming...how much of the [temperature] increase can be ascribed to CO2, to changes in solar activity, or to the natural variability of climate is uncertain

^Dr. David Deming (6 December 2006). "U.S. Senate Committee on Environment & Public Works, Hearing Statements". epw.senate.gov. Retrieved 31 August 2012. The amount of climatic warming that has taken place in the past 150 years is poorly constrained, and its cause – human or natural – is unknown. There is no sound scientific basis for predicting future climate change with any degree of certainty. If the climate does warm, it is likely to be beneficial to humanity rather than harmful. In my opinion, it would be foolish to establish national energy policy on the basis of misinformation and irrational hysteria.

^Idso, Craig D., Idso, Keith E. (1998). "Carbon Dioxide and Global Warming". CO2science.org. Archived from the original on February 24, 2007. Retrieved 16 March 2014. ...there is no compelling reason to believe that the rise in temperature was caused by the rise in CO2. Furthermore, it is highly unlikely that future increases in the air's CO2 content will produce any global warming; for there are numerous problems with the popular hypothesis that links the two phenomena.

^Michaels, Patrick (October 16, 2003). "Posturing and Reality on Warming". CATO Institute. Retrieved June 10, 2009. Scientists know quite precisely how much the planet will warm in the foreseeable future, a modest three-quarters of a degree (Celsius), plus or minus a mere quarter-degree ... a modest warming is a likely benefit... human warming will be strongest and most obvious in very cold and dry air, such as in Siberia and northwestern North America in the dead of winter.